The present invention relates generally to refrigeration systems that use a Stirling cooler as the mechanism for removing heat from a desired space. More particularly, the present invention relates to a glass door merchandiser with a slide-out Stirling refrigeration deck.
In the beverage industry and elsewhere, refrigeration systems are found in vending machines, glass door merchandisers (xe2x80x9cGDM""sxe2x80x9d), and other types of dispensers and coolers. In the past, these units have used a conventional vapor compression (Rankine cycle) refrigeration apparatus to keep the beverages or the containers therein cold. In the Rankine cycle apparatus, the refrigerant in the vapor phase is compressed in a compressor so as to cause an increase in temperature. The hot, high-pressure refrigerant is then circulated through a heat exchanger, called a condenser, where it is cooled by heat transfer to the surrounding environment. As a result of the heat transfer to the environment, the refrigerant condenses from a gas back to a liquid. After leaving the condenser, the refrigerant passes through a throttling device where the pressure and temperature of the refrigerant are reduced. The cold refrigerant leaves the throttling device and enters a second heat exchanger, called an evaporator, located in or near the refrigerated space. Heat transfer with the evaporator and the refrigerated space causes the refrigerant to evaporate or to change from a saturated mixture of liquid and vapor into a superheated vapor. The vapor leaving the evaporator is then drawn back into the compressor so as to repeat the cycle.
Stirling cycle coolers are also a well known as heat transfer mechanisms. Briefly, a Stirling cycle cooler compresses and expands a gas (typically helium) to produce cooling. This gas shuttles back and forth through a regenerator bed to develop much greater temperature differentials than may be produced through the Rankine compression and expansion process. Specifically, a Stirling cooler uses a displacer to force the gas back and forth through the regenerator bed and a piston to compress and expand the gas. The regenerator bed may be a porous element with a large thermal inertia. During operation, the regenerator bed develops a temperature gradient. One end of the device becomes hot and the other end becomes cold. See David Bergeron, Heat Pump Technology Recommendation for a Terrestrial Battery-Free Solar Refrigerator, September 1998. Patents relating to Stirling coolers include U.S. Pat. Nos. 5,678,409; 5,647,217; 5,638,684; 5,596,875 and 4,922,722 (all incorporated herein by reference).
Stirling cooler units are desirable because they are nonpolluting, efficient, and have very few moving parts. The use of Stirling coolers units has been proposed for conventional refrigerators. See U.S. Pat. No. 5,438,848 (incorporated herein by reference). However, it has been recognized that the integration of a free-piston Stirling cooler into a conventional refrigerated cabinet requires different manufacturing, installation, and operational techniques than those used for conventional compressor systems. D. M. Berchowitz et al., Test Results for Stirling Cycle Cooler Domestic Refrigerators, Second International Conference. As a result, the use of the Stirling coolers in, for example, beverage vending machines, GDM""s, and other types of dispensers, coolers, or refrigerators is not well known.
For example, Stirling coolers by their nature produce a small amplitude vibration. Care must be taken to isolate vibrationally the Stirling cooler unit from the cabinet. If vibrations are transmitted from the Stirling cooler unit to the cabinet, the results may range from an annoying noise to even a potential reduction in the life of the refrigeration device as a whole.
A need exists, therefore, for adapting Stirling cooler unit technology to conventional beverage vending machines, GDM""s, dispensers, coolers, refrigerators, and the like. Specifically, the Stirling cooler units used therein should be easily accessible in case of repair or replacement. Preferably, the Stirling coolers should be accessible with a minimum of down time for the enclosure as a whole and without the need for emptying the enclosure. The beverage vending machine, GDM, or other type of dispenser, cooler, or refrigerator with the Stirling cooler units therein should be both easy to use and energy efficient. The Stirling cooler units also should be positioned therein so as to produce a minimum of vibration to the enclosure as a whole.
The present invention thus provides for a refrigerator. The refrigerator may include a cabinet and a refrigeration deck slidably positioned within the cabinet. The refrigeration deck may include a Stirling cooler unit.
Specific embodiments of the invention may include the use of a number of Stirling cooler units. The Stirling cooler units may be free piston Stirling cooler units. One of the Stirling cooler units may be operated out of phase with a second one of the units so as to cancel out the vibrations produced by all of the Stirling cooler units. The Stirling cooler units may each include a fan, a hot end, and a cold end. A hot air shroud may be positioned adjacent to the hot end and a cold end heat exchanger may be positioned adjacent to the cold end. The cold end heat exchanger may include a plate and a number of fins attached thereto. The cold end of the Stirling cooler unit may be attached to the cold end heat exchanger via an attachment ring.
The cabinet may include a refrigerated space and an air plenum such that the air may circulate through the air plenum between the refrigerated space and the refrigeration deck. The air plenum may include a return air stream and a supply air stream. The refrigeration deck may include a cold air shroud positioned adjacent to the air plenum. The refrigeration deck also may include a fan positioned within the cold air shroud so as to circulate the air through the cabinet and the refrigeration deck.
The refrigeration deck may include a base plate with a number of runners thereon so as to slide the refrigeration deck in and out of the cabinet. The runners each may include an isolation pad. The refrigeration deck also may include a vertical wall extending from the base plate. The vertical wall may include an aperture therein. The aperture may be sized to accommodate a Stirling cooler unit therein. An insulation plug also may be positioned within the aperture.
The refrigeration deck may include an isolation mechanism. The isolation mechanism may support the Stirling cooler unit. The isolation mechanism may include an elastomeric layer positioned on a tray. The Stirling cooler unit may include a pin and a vertical plate with a screw positioned thereon. The tray may include an up-turned tab with an unthreaded hole and a down-turned tab with a threaded hole. The pin may engage the unthreaded hole of the upturned tab and the screw may pass through the vertical plate and into the threaded hole of the down-turned tab.
A further embodiment of the present invention may provide for a refrigerator. The refrigerator may include a cabinet and a refrigeration deck. The refrigeration deck may include a number of Stirling cooler units. One of the Stirling cooler units may be out of phase with a second one of the units so as to cancel out the vibrations produced by the Stirling cooler units as a whole.
The refrigeration deck may include a number of isolation mechanisms. Each of the isolation mechanisms may support one of the Stirling cooler units. Each of the isolation mechanisms may have an elastomeric layer positioned on a tray. The refrigeration deck may have a base plate with a number of isolation pads thereon. The refrigeration deck also may include a vertical wall extending from the base plate. The vertical wall may include an aperture therein. The aperture may be sized to accommodate the Stirling cooler unit therein. The aperture also may include an insulation plug.
A further embodiment of the present invention may provide for a refrigeration deck for a refrigerator. The refrigeration deck may include a surface extending in a first direction and a second surface extending in a second direction. The second surface may be connected to the first surface. The second surface may include an aperture therein and an isolation tray positioned thereon. A Stirling cooler unit may be positioned on the isolation tray and extend through the aperture in the second surface.
These and other objects, features, and advantages of the present invention will become apparent after review of the following detailed description of the disclosed embodiments and the appended drawings and claims.